Tap changer rotary switch with radially spaced movable contact members and motion limiting means



April 6, 1965 H. .WEB ETAL 3,177,307

TAP CHANGER ROTARY W TCH WI RADIALLY SPACED MOVABLE CONTACT MEMBERS ANDMOTION LIMITING MEANS Filed Sept. 6. 1961 E I H1 United States Patent M3,177,307 TAP CHANGER RUTARY SWITCH WITH RADI- ALLY SPAQED MOVABLECGNTACT MEMBERS AND MUTIUN LIP /HTTNG MEANS Hans J. Weber and Charles E.Glatz, Pittsburgh, Pa, assignors to Allis=Chahners ManufacturingCompany, Milwaukee, Wis.

Filed Sept. 6, 1961, Ser. No. 136,264 1 Claim. (Cl. 20011) Thisinvention relates to a switch for electrical apparatus and in particularto a rotary type switch designed for handling heavy currents and highvoltages found in such apparatus as line transmission transformers.

Where it is desired to make a variety of circuit connections involvingseveral stationary contacts a general practice has been to provide arotary type switch. The stationary contacts are arranged in a circularpattern with a movable contact pivotably mounted at the center of thestationary contacts. Some of the many requirements for this type ofswitch is that the movable contact and the stationary contacts, inaddition to having long life, exert high pressure against each other.The movable contact should also be self-aligning on the stationarycontacts and apply a strong wiping action against them. Mechanicalstresses should also be absorbed by the switching mechanism in orderthat the mechanism has a high life expectancy. In power circuits thecontact areas should be substantial and adequate clearances should beprovided between the stationary contacts to avoid flashovers.

The switch of this invention embodies all of the above mentionedfeatures with only a minimum number of parts. Briefly, it comprises aplurality of contact posts mounted in an arcuate pattern on aninsulating panel. A pair of movable contacts, mounted in a contactholder which is pivotably fixed to the center of the insulating panel,straddle the contact posts. A biasing means disposed between the twomovable contacts assures their making good connection with the contactposts.

It is therefore one object of this invention to provide a new andimproved electrical switch.

Another object of the invention is to provide a new and improved rotaryswitch for making a number of circuit connections.

Another object of this invention is to provide a new and improved switchsuitable for high voltage applications.

Objects and advantages other than those mentioned above will be apparentfrom the description when read in connection with the drawing in which:

FIG. 1 is a front view in elevation of the switch of this invention;

FIG. 2 is a cross section taken along the lines IIII of FIG. 1;

FIG. 3 is a schematic showing of the switch of this invention applied tothe tapped windings of a transformer, and

FIG. 4 is an isometric view of the switch.

As shown in FIGS. 1 and 2, an insulating panel 11 supports sixstationary contact posts 14 arranged in a circular pattern. Ifpreferred, the posts 14 may be arranged in an arcuate pattern other thancircular. The panel 11 may be of any standard insulating material suchas a phenolic or polyester substance and if desired may be stamped ormolded into the illustrated design. For improved dielectric properties,elongated apertures 21 may be formed between each of the stationarycontact posts, taking care that these apertures are not of such a sizeas to materially reduce the strength of the panel. At the base of thepanel are two spaced mounting members 23 with juxtaposed right angleshoulders 24. With the provision of the shoulders the panel may besnugly mounted on a rectangular insulating support 26 of sufli-3,177,307 Patented Apr. 6, 1965 cient structural strength and securedthereto by a bolt 28 extending through the base mounting members 23 andthe support 26.

While the illustrated embodiment of this invention shows six stationarycontact posts 14, it is to be understood that a greater or lesser numbermay be used if arranged in an arcuate pattern. These posts may be formedfrom one of the numerous electrical conductive materials available andmay either be molded in with the insulating panel 11 or fixed separatelyto it as illustrated. Each contact post 14 contains a shoulder element30 which abuts the rear side 31 of the panel. The posts extend throughthe panel 11, and at a point approximately flush to the front 34 of thepanel have an indentation (not visible) for seating a lock washer 33.Permanent electrical connections between each post and its correspondinglead 35 may be accomplished through crirnps 36 or conventional fasteninghardware.

Extending through the center point of the circular arranged posts is anoperating shaft 39. The shaft 39 is journaled for rotation in the panel11. Fixed to the rectangular end 51 of the shaft is a contact holder 43.In the particular instance this is accomplished by providing arectangular hole 44 through the fixed end 46 of the contact holder 4-3so that it is complementary with a rectangular portion of the shaft end41. A roll pin 47 may be inserted through the fixed end 46 of thecontact holder and the shaft end 41 to prevent displacement of thecontact holder 43.

The contact holder has a pair of spaced parallel tines 49 radiallyextending from the center of the contact posts 14. Slidably mountedbetween the two tines 49 along their longitudinal axis are a pair ofjuxtaposed inner and outer contacts 51 and 52. The sliding action of thetwo contacts is radial and is accomplished with pins 54 extendingthrough sides 55 of the contacts at an intermediate point and intoelongated apertures 57 in the two tines Q9. The two inner ends 58 of thetwo contacts 51 and 52 straddle a pair of the contact posts 14. Eachinner end 58 has a projected face 66 for making contact with two of thecontact posts. Outer end 62 of each contact 51 and 52 has a shoulder 63.Positioned between the juxtaposed shoulders 63 is a compressed spiralspring 64. T o avoid current flow through the spring which mayprematurely age it, insulation 65 may be provided at one end. One of anumber of ways for aligning the spring 64 and limiting the amount ofmovement between the two contacts may comprise an insulating cylinder 67contained within the spiral spring 64 and seats 65. The compressedspring 64 exerts force against each of the outer ends 62 of the contacts5i and 52 and in turn the inner ends 58 of the contacts are forcedsolidly against a pair of the contact posts 14.

It is to be noted that each of the contacts 51 and 52 is curved and isconcentric to the circle defined by the stationary contact posts 14-.The outer contact 52 is longer than the curved inner contact 51 due tothe perimeter differences. Because the current flows in the samedirection in each of the parallel contacts Si and 52., a magnetic forceis present which tends to pull the two contacts more solidly against apair of contact posts 1- in order to obtain an equal division of currentin the two contacts 51 and 52 and therefore maximum attraction betweenthem, the longer outer contact 52 is provided with a greater crosssectional area. The ratio of the cross sectional areas of the twocontacts 51 and 52 is approximately the same as the inverse ratio oftheir current carrying lengths in order to get maximum attraction. Thus,with the combination of the forces of the spring 64 and the compressionand the magnetic forces acting on the contacts 51 and 52, positivepressure is exerted on the contact posts 14.

In FIG. 3 a transformer 69 is schematically illustrated with a primarywinding 70 and a tapped two section secondary winding 71. Leads 35 fromthe tapped sections of the secondary winding are fixed to the stationarycontact posts 14. By operating the movable contacts 51 and 52 about theposts 14 varying amounts of the secondary winding 71 are added andsubtracted and a variety of voltages may be obtained. A conventionallever or handle, not illustrated, may be secured to rectangularprojection 73 of contact holder 43 for movement of contacts 51 and 52about the posts 14.

While only one embodiment of the present invention has been illustratedand described, it Will be apparent to those skilled in the art thatmodifications other than those mentioned above may be made withoutdeparting from the spirit of the invention or from the scope of theappended claim.

Having now particularly described and ascertained the nature of our saidinvention and the manner in which it is to be performed, we declare thatwhat we claim is:

An electric switch comprising: an insulating panel; a plurality ofgenerally parallel contact posts mounted in an arcuate pattern on saidpanel; a radially extending contact holder mounted at the center of saidcontact posts to rotate on an axisgenerally parallel to said posts, saidholder having a fork member with a pair of spaced parallel tines; a pairof radially spaced juxtaposed contacts positioned between said tines forrotation from post to post, each said juxtaposed contact having a pinlaterally extending through an intermediate section, each said pin beingsupported in an elongated aperture longitudinally aligned in each ofsaid tines, one axially displaced end of each of said juxtaposedcontacts comprising an arcuate length straddled across a pair ofadjacent contact posts, the opposite axially displaced end of each ofsaid juxtaposed contacts having a biased compression spring disposedtherebetween and urging said juxtaposed contacts against said adjacentposts; and means positioned between said juxtaposed contacts and havinga length slightly less than the space between said juxtaposed contactsfor limiting their relative motion;

References Cited by the Examiner UNITED STATES PATENTS 593,286 11/97Waite ZOO-11 1,752,213 3/30 Treanor. 2,078,331 4/37 Leidy. 2,604,5567/52 Daly et al y 200-15 X 2,686,236 8/54 Hodtum 20011 2,760,017 '8/ 5 6Stenersen 200-11 2,918,541 12/59 Waite 200-11 2,921,996 1/60 DuludeZOO-11 BERNARD A. GILHEANY, Primary Examiner.

